1. Field of the Invention
The present invention relates to a film-forming apparatus and a film-forming method for forming a thin film by sputtering.
2. Description of the Related Art
In general, in a process of manufacturing a semiconductor device, a display device, an illumination device, an imaging device, and other electronic and optical components, a thin-film forming technology is indispensable. As a method of forming a thin film, a sputtering method is well known. The thin-film forming technology using sputtering has such advantages that a thin film can be formed at low temperature, that a thin film having a large area can be formed, and that electric control of film-forming parameters is performed easily.
The sputtering method is performed by a sputtering apparatus. According to such a sputtering method, accelerated ions are irradiated to a target so that target particles are ejected from the target, and the target particles are deposited on a silicon wafer or a glass substrate in a thin film shape.
The thin-film forming technology using sputtering has a number of superior aspects in terms of performance compared with an evaporation method or chemical vapor deposition (CVD), but an apparatus mechanism may become complicated. For example, a conventional sputtering apparatus 71 provided with multiple (for example, three) targets is described with reference to FIG. 9 as a schematic view.
As illustrated in FIG. 9, the conventional sputtering apparatus 71 has a vacuum chamber 72. A substrate holder 32 that functions as an anode with one end thereof grounded is placed in an upper part of the vacuum chamber 72, and a substrate 31 is removably held by the substrate holder 32. A film to be formed on a lens used as the substrate 31 is an antireflection film of a general optical component, which is a multilayered film made of, for example, Ta2O5, SiO2, and Al2O3.
Cathode mechanisms 21, 22, and 23 are placed in a center part of the vacuum chamber 72, and a DC high-voltage power supply (hereinafter, referred to as “DC power supply”) 51 capable of applying a high voltage through power supply switches 3, 4, and 10 is connected to the cathode mechanisms 21, 22, and 23. A negative electrode of the DC power supply 51 is connected to the power supply switches 3, 4, and 10 side, and a positive electrode of the DC power supply 51 is grounded. The cathode mechanisms 21, 22, and 23 are placed in parallel, and targets 11, 12, and 13 are removably mounted to upper portions of the cathode mechanisms 21, 22, and 23, respectively. The target 11 is formed of Ta, the target 12 is formed of Si, and the target 13 is formed of Al.
In an upper part of the vacuum chamber 72, shutters 41, 44, and 43 made of SUS stainless steel are placed separately between the targets 11, 12, and 13 and the substrate 31. The shutter 41 is connected to a driving device 5 placed outside the vacuum chamber 72 and configured so as to move forward and backward with a predetermined space ensured above the target 11. The shutter 44 is connected to a driving device 6 placed outside the vacuum chamber 72 and configured so as to move forward and backward with a predetermined space ensured above the target 12. The shutter 43 is connected to a driving device 9 placed outside the vacuum chamber 72 and configured so as to move forward and backward with a predetermined space ensured above the target 13. As illustrated in FIG. 9, plasma 721 is generated on the target 12.
In the conventional sputtering apparatus 71, the cathode mechanisms 21, 22, and 23 are required separately for the Ta target 11, the Si target 12, and the Al target 13, which renders the mechanism complicated and also increases the apparatus cost (see Japanese Patent Application Laid-Open Nos. H07-331432 and 2003-113467).
By the way, even regarding optical components to be used in the same imaging device, an increase in an apparatus cost is acceptable in an industrial product such as a semiconductor exposure device in which performance is prioritized compared with a cost, whereas a cost is most prioritized in the case where an optical component is used in a camera or broadcasting equipment for general consumers. Further, in thin-film formation in an optical component, it is necessary to use an apparatus capable of sputtering multiple (at least two kinds of) materials, for example, in the case of manufacturing an antireflection film.
However, in order to sputter multiple materials, targets and mechanisms on the periphery of cathodes accompanying the targets need to be placed in the sputtering apparatus in accordance with the number of the materials. As a result, the apparatus cost increases in accordance with the number of the mechanisms, and further, the apparatus is enlarged in accordance with the volumes of the mechanisms, which may increase the apparatus cost.